Fortress - Yosai

A defensive military facility built to increase the tactical value of a certain area. Broadly speaking, there are permanent fortifications and field fortifications. The act of fortification is called fortification, and a line of many fortifications is called a fortification line. Permanent fortifications are solid positions built above and below ground in important coasts, ports, borders, islands, and urban areas during peacetime, and are equipped with artillery, gun emplacements, obstacles, communication, observation, medical, and residential facilities, as well as warehouses and transportation routes, and are comprehensively constructed to withstand long-term attacks from land, sea, and air, and to serve as a base for attacks. They are classified into border, coastal, island, and strategic fortifications. They are built using metal, stone, concrete, brick, soil, and other materials, and are constructed over a long period of time and at great expense. Field fortifications are built with makeshift materials in a relatively short time on the battlefield close to the enemy, and are inferior in strength and defensive power to the former, but are often reinforced and turned into permanent fortifications as the battle becomes stalemated.

There have been many sturdy castles and forts since ancient times, but some representative examples of modern forts are the Sevastopol Fortress from the Crimean War, the Russian Port Arthur Fortress from the Russo-Japanese War, which boasted a 150-day endurance, the French Verdun Fortress from World War I, the British Hong Kong Fortress and Singapore Fortress from World War II, and the American Corregidor Fortress. Fortification lines include the Hindenburg and Siegfried Fortresses of Germany, the Maginot Fortress of France, and the Stalin Fortress of the Soviet Union. Japan also had coastal forts such as the Tokyo Bay Fortress, which originated from Odaiba, the border fort of Koto in Manchuria (northeastern China), and island forts such as the Tsushima Fortress, but no battles were fought there except for the Koto Fortress. Currently, the strategic value of fortresses is gradually declining due to a lack of mobility, the appearance of nuclear weapons, and the development of aircraft.

[Terada Chikao]

“Japanese Castle Construction History” written by Asami Joboji (1971, Hara Shobo)

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

ある地域の戦術的価値を高めるために構築された防御的軍事施設。大別して永久要塞と野戦要塞がある。またその行為を要塞化といい、多数の要塞の連なった線を要塞線という。永久要塞は、平時から重要な海岸、港湾、国境、島、都市要地などの地上と地下に堅固な陣地を構築し、砲台、銃座、障害物、通信、観測、医療、居住の各設備や倉庫、交通路を備え、地上、海上、空中からの攻撃に長期的に耐え、また攻撃の拠点となるよう総合的に構成されている。国境、沿岸、島嶼(とうしょ)、要地の各要塞に分類される。構築材としては金属、石、コンクリート、れんが、土砂などで、多大の月日と費用をかけて構築される。野戦要塞は、敵と近接する戦場で比較的短時日に応急的材料で構築するもので、前者に比べて強度や防御力は劣るが、戦闘の膠着(こうちゃく)化につれて補強され、永久要塞化されることが多い。

　古代から堅固な城塞や砦(とりで)は数多いが、近代的要塞の代表例は、クリミア戦争時のセバストポリ要塞、150日間の持久力を誇った日露戦争時のロシアの旅順(りょじゅん)要塞、第一次世界大戦時フランスのベルダン要塞、第二次大戦時イギリスの香港(ホンコン)要塞・シンガポール要塞、アメリカのコレヒドール要塞。要塞線では、ドイツのヒンデンブルク、ジークフリート、フランスのマジノ、ソ連のスターリンなど。また日本では、お台場に起源する東京湾要塞などの沿岸要塞、満州（中国東北部）虎頭(ことう)の国境要塞、対馬(つしま)要塞などの島嶼要塞があったが、虎頭要塞以外は戦闘はなかった。現在、要塞の戦略的価値は、機動力の欠如、核兵器の登場、航空機の発達などにより、しだいに低下しつつある。

［寺田近雄］

『浄法寺朝美著『日本築城史』（1971・原書房）』

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